1. Field of the Invention
The present invention relates to an oxygen supply apparatus capable of supplying oxygen or oxygen-enriched gas to, for example, a patient, synchronously with breathing of the patient. The present invention further relates to a controller for the oxygen supply apparatus and to a recording medium for the controller.
2. Description of the Related Art
Examples of conventional known apparatuses for supplying high-concentration oxygen to a patient include an oxygen cylinder filled with oxygen gas, and an oxygen enriching apparatus for medical use capable of producing oxygen-enriched gas from, for example, air through adsorption removal of nitrogen contained in the air and supplying the gas to a patient.
Of these, the oxygen enriching apparatus is used by, for example, a patient who recuperates his/her health over a long time at home, because the oxygen enriching apparatus can supply oxygen-enriched gas over a long time. Since a patient who uses such an oxygen enriching apparatus is weak in lung function as compared with healthy persons, the patient must use the oxygen enriching apparatus all day long. Thereforee, an oxygen enriching apparatus which can be used conveniently for daily living has been in demand.
Meanwhile, since the oxygen cylinder is small in size and is easy to carry about, the oxygen cylinder is used as a portable apparatus which a patient carries with him or her during travel or at the time of visiting a hospital.
Since such an oxygen cylinder has a limited supply of oxygen, a breath synchronizer for supplying oxygen synchronously with breathing is used so as to reduce consumption of oxygen supplied from the cylinder, to thereby extend the service life of the oxygen cylinder.
The breath synchronizer utilizes the rule of thumb that in the case of a human the ratio between the inhalation period and the exhalation period is 1:2. Upon detection of inhalation by means of a sensor, the breath synchronizer supplies high-concentration oxygen from the oxygen cylinder over a short period of time (in the manner of a pulse).
In recent years, a technique has been proposed for applying to an oxygen enriching apparatus the breath synchronization technique used with an oxygen cylinder (see, for example, Japanese Patent Application Laid-Open (kokai) No. 8-187289).
3. Problems to be Solved by the Invention
When oxygen is supplied by means of the above-described breath-synchronized operation, a timing of start of inhalation is detected by use of, for example, a pressure sensor, and oxygen is supplied during the inhalation period. However, in some cases, the timing of start of inhalation cannot be detected due to a certain cause.
Therefore, a situation may occur in which oxygen cannot be supplied at proper timings, and a measure for such a situation is required.